"They can act like chickens, they can run around," says Kesten, who's raising hens in an old wooden shed in the open countryside near Concordia, Mo. "They can go out and catch bugs, they can dig in the ground."

But most U.S. hens live crammed into very close quarters, according to Joe Maxwell, with the Humane Society of the U.S. And he says that's just wrong.

"There are some things we should not do to animals," says Maxwell.

California voters felt the same way, and six years ago they passed Proposition 2, requiring California producers to provide cages that are almost twice as large as most chickens have now. The Legislature followed that with a law requiring that all eggs sold in California be raised under those conditions.

"We can't have our farmers and ranchers at the whim of California's voters, and that's why we filed the lawsuit," says Bruning.

Their chief complaint is that their egg producers must either spend millions to comply with California restrictions, or face being shut out of that enormous market.

Don Nikodim with the Missouri Pork Association calls it "a clear violation of the U.S. Commerce Clause."

Now, why would pig farmers care about henhouse restrictions?

Because when a huge state like California slaps restrictions on food it imports, farmers all over the country become alarmed. And Nikodim says this won't likely stop with eggs.

"Logically, the next step is, we should extend our authority on how you produce pork to other states as well," he says. "Then is it dairy, is it beef, is it corn — go down the list."

Nikodim is worried that restrictions on cramped pig stalls, called gestation crates, may come next. Blake Hurst, with the Missouri Farm Bureau, says if this kind of thing goes unchecked, farmers could soon face a mishmash of state laws.

"It's important because of the precedent set," says Hurst. "It's not important because of how chickens are housed."

The egg lawsuit isn't the first effort to try to blunt state-specific livestock restrictions. Last year, Rep. Steve King, R-Iowa, tried to amend the Farm Bill to nullify restrictions like California's Proposition 2.

"We just simply cannot let California dictate to the rest of the country how we house hens or hogs or cattle," says King.

But a coalition of animal welfare organizations and environmentalists killed the King amendment, according to Maxwell.

Meanwhile, in California, egg producers are gearing up to comply with the new law when it kicks in Jan. 1. Jill Benson, whose great-grandfather started JS West, an egg producer with hundreds of thousands of birds, says many of them now enjoy nearly double the space they had before.

"And you see perches, nest boxes, scratch areas, emery boards and a number of accoutrements where the bird is able to display more of her natural behaviors," says Benson.

As you'd expect, comparatively spacious chicken accommodations are more expensive to build, but over years the cost turns out to be about a penny an egg.

Well, that's what the egg industry was saying last year in a video that was part of a campaign by the United Egg Producers to mandate cages compliant with California law nationwide.

Jo Manhart, with the Missouri Egg Council, says egg producers had agreed to a uniform national standard with their old adversary the Humane Society. The resulting Egg Bill drew lots of support but ran into a wall of opposition from the meat industry.

"They did not want this deal to go through because they felt it would affect them later on, and I think it would," Manhart says. "So, that's dead."

The death of the Egg Bill, and the King amendment, set up the current lawsuit in a U.S. District Court. And the ruling will almost certainly be appealed.

After all, there's a lot at stake in a battle pitting state against state, and big ag against powerful animal welfare groups. The money involved could be in the billions. And that ain't chicken feed.

California has hatched a law that will go into effect next year. It requires all eggs sold in the state to come from hens living in cages that are almost twice as large as the ones most chickens have now. So far, six states are suing to protect their farmers from having to comply with those California restrictions.

As Frank Morris from member station KCUR reports, the fight is about a lot more than the size of a hen house.

FRANK MORRIS, BYLINE: By most measures, David Kesten's hens are living the good life.

DAVID KESTEN: Oh, they can act like chickens, they can run around. They can go and catch bugs, they can dig in the ground.

MORRIS: These 1-percenters strut around an old wooden shed in the open countryside near Concordia, Missouri while most U.S. hens live crammed into very close quarters, according to Joe Maxwell, with the Humane Society of the United States.

JOE MAXWELL: That is just wrong. There are some things we just shouldn't do to animals.

MORRIS: California voters felt the same way and six years ago, they passed Proposition 2, requiring California producers to provide more space for hens. The legislature followed that with a law requiring all eggs sold in California be raised under those conditions.

ATTORNEY GENERAL JON BRUNING: Very, very troubling. We can't have our farmers and ranchers at the whim of California's voters, and that's why we filed the lawsuit.

MORRIS: Nebraska Attorney General Jon Bruning and five other Attorneys General had joined a lawsuit against California. Their chief complaint is that their egg producers must either spend millions to comply with California restrictions, or face being shut out of that enormous market.

DON NIKODIM: That's a clear violation of the United States commerce clause.

MORRIS: That's Don Nikodim with the Missouri Pork Association.

Now, why would pig farmers care about henhouse restrictions? Because when a huge state like California slaps restrictions on food imports, farmers all over the country become alarmed. And Nikodim says, this won't likely stop with eggs.

NIKODIM: So, logically the next step is, well, we should extend our authority on how you produce pork to other states, as well. Then is it dairy, is it beef, is it corn? Go down the list.

MORRIS: Nikodim is worried that restrictions on cramped pig stalls, called gestation crates maybe next. Blake Hurst, with the Missouri Farm Bureau, says if this kind of thing goes unchecked, farmers could soon face a mishmash of state laws.

BLAKE HURST: this is important because of the precedent set. It's not important because of how chickens are housed.

MORRIS: The egg lawsuit isn't the first effort to blunt state-specific livestock restrictions. Last year, Iowa congressman Steve King tried to amend the Farm Bill to nullify restrictions like California's Prop 2.

REPRESENTATIVE STEVE KING: So we just simply cannot let California dictate to all the rest of the country, how we house hens, or hogs or cattle.

MORRIS: But a coalition animal welfare organizations and environmentalists killed the King amendment, according to Joe Maxwell.

MAXWELL: They couldn't win legislatively, so they're going to try a judiciary track to preempt state's rights to regulate health and safety and animal welfare issues. King amendment round two.

MORRIS: Meanwhile, in California, egg producers are gearing up to comply with the new law when it kicks in January 1st. Jill Benson, whose great grandfather started JS West, an egg producer with hundreds of thousands of birds, says many of them now enjoy nearly double the space they had before.

JILL BENSON: Then you see perches, nest boxes, scratch areas, emery boards, and a number of accoutrements like that - if you will - where the bird is able to display more of her natural behaviors.

MORRIS: As you'd expect, comparatively spacious chicken accommodations are more expensive to build, but over years, the cost turns out to be about a penny an egg.

(SOUNDBITE OF PROMOTIONAL VIDEO)

UNIDENTIFIED WOMEN: One Penny?

UNIDENTIFIED WOMAN: Small price to pay to ensure a better life for me and my hen girlfriends, right?

MORRIS: Well, that's what the egg industry was saying last year in this video was part of a campaign by the United Egg Producers to mandate cages compliant with California law nation-wide.

Jo Manhart, with the Missouri Egg Council, says egg producers had agreed to uniform national standard with their old adversaries, the Humane Society. The resulting egg bill drew lots of support but ran into a wall of opposition from the meat industry.

JO MANHART: They did not want this deal to go through because they felt that it would affect them later on, and I think it would. So, that's dead.

MORRIS: So, the death of egg bill and the King amendment set up the current lawsuit in U.S. District Court. And the ruling will almost certainly be appealed.

After all, there's a lot at stake in a battle pitting state against state and big ag against powerful animal welfare groups. The money involved could be in the billions, and that ain't chicken feed.